Circuit breaker

ABSTRACT

A circuit breaker having a bimetallic member normally in a circuit closed position in which it engages a stationary terminal to provide a conductive path therebetween, but which is movable toward a circuit open position when heated in response to an electric current in excess of a predetermined magnitude being passed therethrough. The circuit breaker also includes a resistance heater in the form of a printed circuit bonded to the bimetallic member and which is in a parallel circuit with the bimetallic member. When the bimetallic member is moved toward its circuit open position the current flows through the resistance heater to maintain the bimetallic member in a heated condition and in its circuit open position.

United States Patent [72] inventor Richard J. Hanson FOREIGN PATENTS m Al N g g? 1,151,859 5/1969 Great Britain 337/107 0. E 53 18 1970 PrimaryExaminer-Bernard A. Gilheany [45] Patented Dem 21 1971 AssistantExaminer-Dewitt M. Morgan [73 1 Assignee Gum. Motors corponfionAttorneys-W. E. Finken and W. A. Schuetz Detroit, Mich.

ABSTRACT: A circuit breaker having a bimetallic member [54] CIRCUITBREAKER normally in a circuit closed position in which it engages a sta-4 Chin, 5 Drawing Figs. gormrzl termmal to tplroitnde adconductue paththerebetwe'fn, u w 1c is mova e owar a c1rcu1 open pos1t1on w en [52]US. Cl 337/103, heated in response to an electric current in excess of a337/107 337/1 13 predetermined magnitude being passed therethrough. Thecir- [51] II. C ..ll0lh37/54, cuit breaker also includes a resistanceheater in the form of a 61/013 61/04 printed circuit bonded to thebimetallic member and which is FIG oiSearch in a parallel circuit withthe bimetallic member. w the 1 381 bimetallic member is moved toward itscircuit open position [56] Rehnnm Cited the current flows through theresistance heater to maintain the UNnED STATES PATENTS bimetallic memberin a heated condition and in its circuit open osition. 2,403,803 7/1946Kearsley 337/ I03 UX p /d I0 .49 a

CIRCUIT BREAKER The present invention relates to a circuit breaker, andin particular to a circuit breaker having a bimetallic member whichismovable toward a circuit open position when heated in response to acurrent in excess of a predetermined magnitude passing therethrough.

l-leretofore, bimetallic circuit breakers have been provided forbreaking an electric circuit when current in excess of a predeterminedmagnitude was passed therethrough. These circuit breakers comprised abimetallic member operatively connected to a load device and astationary contact operatively connected with a power source, or viceversa. The bimetallic member was normally disposed in a circuit closedposition in which it engaged the stationary contact to provide aconductive path therethrough. However, when the current passing throughthe bimetallic member exceeded a predetermined magnitude, the bimetallicmember was heated which caused the same to be moved away from thestationary contact to break the electric circuit. When the bimetallicmember cooled, it returned toward its circuit closed position.

It is also known in the art to provide auxiliary heating means to keepthe bimetallic member heated and in its circuit open position. Theseauxiliary heaters were connected in parallel with the bimetallic member,but were separate therefrom. When the bimetallic member moved to itscircuit open position the current passed through the resistance heaterto maintain the bimetallic member in a heated condition. An advantage ofthis latter type of circuit breaker is that it remains in its circuitopen position until the current from the power source is shut off.Bimetallic circuit breakers having such auxiliary heating means areshown in US. Pat. Nos. 1,830,578, l,70l ,757, 2,884,50] and 3,265,839.

The present invention provides a new and improved bimetallic circuitbreaker which is more compact than known circuit breakers and which hasan auxiliary resistance heater in the form of a printed circuit bondeddirectly onto an insulated portion of the bimetallic element. Thecurrent is normally shunted through the bimetallic element when it is inits normal circuit closed position, but passes through the printedcircuit resistance heater when the bimetallic element moves to a circuitopen position to maintain the bimetallic element in the latter position.

Accordingly, it is a broad object of the presentinvention to provide anew and improved bimetallic type circuit breaker which is of a compactconstruction and which includes an auxiliary resistance heater in theform of a printed circuit secured or bonded directly onto the bimetallicelement to heat the latter and maintain it in its circuit open positionupon being moved thereto.

Another object of the present invention is to provide a new and improvedcircuit breaker having a stationary terminal, a bimetallic member whichis normally disposed in a circuit closed position in which a contactsurface thereon engages the terminal, but which is movable toward acircuit open position when heated in response to a current in excess ofa predetermined magnitude being passed therethrough, and a resistanceheater in the form of a printed circuit bonded on an electricallyinsulated portion of the bimetallic member and having a first contactsurface in electrical engagement with the bimetallic member and a secondcontact surface biased by said bimetallic member into constantelectrical engagement with a curved contact surface on the stationaryterminal, and wherein the second contact surface of the resistanceheater rolls on the curved contact surface of the stationary terminalwhen the bimetallic element is moved to its circuit open position, thecurrent passing through the resistance heater to maintain the bimetallicelement heated when the latter is in its circuit open position.

The present invention further resides in various novel constructions andarrangement of parts, and further objects, novel characteristics andadvantages of the present invention will be apparent to those skilled inthe art to which it relates and from the following detailed descriptionof the illustrated embodiment hereof made with reference to theaccompanying drawings forming a part of this specification and in whichsimilar reference numerals or characters are employed to designatecorresponding parts throughout the several views, and in which:

FIG. 1 is an elevational view, with portions shown in section, of thenovel circuit breaker of the present invention;

FIG. 2 is a plan view of part of the circuit breaker shown in FIG. 1;

FIG. 3 is an end elevational view of the circuit breaker shown in FIG.1;

FIG. 4 is an enlarged fragmentary view of part of the circuit breakershown in FIG. 1; and

FIG. 5 is an enlarged fragmentary view of part of the circuit breakershown in FIG. 1 and looking in the direction of the arrows 5-5.

As representing an illustrated embodiment of the present invention, thedrawing show a circuit breaker 10. The circuit breaker 10 could be usedin various applications wherein it is desired to interrupt an electriccircuit in response to a current in excess of a predetermined magnitudepassing therethrough. It is particularly useful, however, in automotiveapplications, such as for use as an overload protector for an electricmotor for operating vehicle components, such as a window regulatormechanism.

The circuit breaker 10 comprises, in general, a housing or supportmember 12, a stationary terminal 14 which is adapted to be electricallyconnected to a load device, such as an electric motor, a stationaryterminal 16 which is adapted to be electrically connected to a suitablepower source, such as a battery of a vehicle, a bimetallic member 18which is supported in cantilever fashion by a stationary terminal 16,and a resistance heater 20 bonded to the bimetallic member 18 and whichis electrically connected in parallel with the bimetallic member 18.

The housing or support 12 could be of any suitable shape orconstruction, but is here shown as comprising a hollow member made froma suitable electrically insulating material. The housing 12 comprises apair of end portions 12a and 12!) having transverse or radiallyextending slots 21 and 22 therein, respectively, and an annularintermediate portion which defines a chamber 23. The housing 12 has anopening 24 along a side portion thereof which is in communication withthe chamber 23.

The stationary terminal 14 comprises an elongated flat metal blade,preferably steel, which is supported by the housing 12 intermediate itsends. The stationary terminal 14 has a pair of spaced elongated detents14 a which are snap fittingly received within recesses 21a in the endportion 12a of the housing 12 and in communication with the slot 21 tosecurely retain the stationary terminal 14 in place upon the latterbeing inserted sidewise through the slot 21. The stationary terminal 14has a forward portion 14b which extends within the chamber 23 and issupported by the housing 12 in cantilever fashion. The stationaryterminal 16 comprises a flat blade which is secured to the other endportion 12b of the housing 12, and in the same manner as the stationaryterminal 14.

The stationary terminal 16 supports the bimetallic member 18 incantilever fashion. To this end, one end of the bimetallic member iswelded or otherwise secured to the stationary terminal 16. Thebimetallic member 18 is an elongated, flat, thin member and can be madefrom any suitable metallic materials, such as two different steelalloys. The bimetallic member 18 at its free end 18a has a contactsurface in the form of a silver alloy contact 1812 which is engageablewith a contact surface in the form of silver alloy contact 14c locatedintermediate the ends of the stationary tenninal 14.

The bimetallic member 18 is movable between circuit closed and circuitopen positions. The bimetallic member 18 is normally disposed in acircuit closed position, as shown by the solid lines in F 16.1, in whichthe contact 18b engages the contact 14c on the stationary terminal 14 toprovide a conductive path between the stationary terminals 14 and 16 viathe bimetallic element 18. When bimetallic member 18 is in its circuitopen position, as shown by the phantom lines in FIG. 1, the contact 18bis out of engagement with the contact 14c on the stationary terminal 14and thus, the conductive path between the stationary terminals 14 and 16is broken. The bimetallic member 18 is movable from its circuit closedposition towards its circuit open position when the current passingtherethrough exceeds a predetermined magnitude. When the current exceedsa predetermined magnitude it heats the bimetallic member 18 to.atemperature to cause the same to be moved toward its circuit openposition.

In accordance with the provisions of the present invention, a resistanceheater in the form of a printed circuit is provided to maintain thebimetallic member 18 in its circuit open position when the latter hasmoved thereto. As shown in FIG. 5, the printed circuit 20 is in the formof a resistance grid bonded or secured to a layer or film of insulatingmaterial 30, the latter in turn being bonded or secured to the undersideof the bimetallic member 18. The printed circuit 20 is preferably madefrom stainless steel and the insulating material could be any suitablematerial, such as a ceramic layer, or plastic film, such as that soldunder the trademark Kapton.

The printed circuit 20 includes a contact surface or portions 20a whichis in constant electrical engagement with the terminal 16. It alsoincludes a contact surface or portion 20b which is in constantengagement with the upper curved or convex surface 14d of the free endof the stationary terminal 14, The printed circuit 20 is formed by anetching process. lnitially a stainless steel sheet is bonded or securedto the insulated backing layer and then the stainless steel is etched toprovide the grid circuit shown in H0. 5. This type of process is wellknown in the art and hence, will not be described in detail. 7

An important feature of the present invention is that the contactsurface 20b of the printed circuit 20 remains in constant engagementwith the convex surface 14d of the stationary terminal 14 as thebimetallic member 18 moves between its circuit closed and circuit openpositions. This is accomplished by biasing the bimetallic member 18 intoengagement with the surface 14d and by providing a rolling actionbetween the contact surfaces 14d and 20 b when the bimetallic member 18moves between its positions. As can be seen in FIG. 1 and 4, thebimetallic member 18 is caused to be slightly bowed and in opposition tothe self-biasing forces tending to maintain the member 18 planar, whenin its circuit closed position, as a result of the engagement betweenthe free end of the terminal 14 and the bimetallic member 18 adjacentits end connected to the terminal 16. The self-biasing forces of thebimetallic member 18 maintains the contact surface portion 20b of theprinted circuit in engagement with the contact surface 14b.

When the bimetallic member 18 moves toward its circuit open position, asshown by the phantom lines in H6. 1, the contact surface 20b of theprinted circuit rolls on the convex surface 14d of the stationaryterminal 14 so as to remain in engagement therewith. In the circuit openposition the current, which is normally shunted through the bimetallicmember 18 to the stationary terminal 16, passes from the stationaryterminal 16 through the resistance grid 20 to the stationary terminal14. This maintains the bimetallic member 18 in a heated condition and inits circuit open position. The resistance value of the grid iscorrelated to the desired value of the current or amperage passingthrough the circuit so that the value of the current after passingthrough the resistance grid 20 is very low.

When the power source is disconnected from terminal 16, such as byopening a switch between the power source and terminal 16, thebimetallic member 18 will cool and move to its circuit closed position.

Although the illustrated embodiment thereof has been described in greatdetail, it should be apparent that certain modifications, changes, andadaptations may be made in the illustrated embodiment, and that it isintended to cover all such modifications, changes and adaptations whichcome within the spirit of the present invention.

What is claimed is: V

1. A current responsive circuit breaker comprising; a terminal member; abimetallic member; one of said members being adapted to be operativelyconnected to an electrical power source; the other of said members beingadapted to be operatively connected to a load; said bimetallic memberbeing supported in cantilever fashion and having a contact surfaceadjacent its free end which is engageable with said terminal member,said bimetallic member being normally disposed in a circuit closedposition in which said contact surface adjacent its free end engages theterminal member to provide a conductive path therebetween, saidbimetallic member being movable away from said terminal member toward acircuit open position to break the conductive path therebetween inresponse to being heated by passage of a current in excess of apredetermined magnitude therethrough; a layer of electrically insulatingmaterial on a portion of said bimetallic member, a resistance heater inthe form of a printed circuit on said layer, said printed circuit havingfirst and second contact surfaces in constant engagement with a surfaceon said bimetallic member and said terminal member, respectively,whereby when said bimetallic member is in its circuit open position thecurrent is passed through said printed circuit to maintain thebimetallic member in a heated condition and in its circuit openposition, said bimetallic member being self-biased into engagement withthe terminal member and said second contact surface rolls on saidterminal member while maintaining engagement therewith when thebimetallic member moves to its circuit open position.

2. A current responsive circuit breaker comprising: a terminal member; abimetallic member; one of said members being adapted to be operativelyconnected to an electrical power source; the other of said members beingadapted to be operatively connected to a load; said bimetallic memberbeing supported at one end in cantilever fashion and having a contactsurface adjacent its free end which is engageable with said terminalmember, said bimetallic member being normally disposed in a circuitclosed position in which said contact surface adjacent its free endengages said terminal member to provide a conductive path through thebimetallic member, said bimetallic member being movable from saidcircuit closed position toward a circuit open position in which saidcontact surface adjacent its free end disengages the terminal member tobreak the conductive path therethrough in response to being heated bypassage of a current therethrough in excess of a predeterminedmagnitude, a layer of electrically insulating material on a portion ofsaid bimetallic member, a resistance heater in the form of a printedcircuit on said layer, said terminal member having a curved contactsurface, said printed circuit having first and second contact portionsin constant engagement with said bimetallic member and said curvedcontact surface on said terminal, respectively, whereby when saidbimetallic member is moved toward its circuit open position the currentwill be passed through the resistance heater to maintain the bimetallicmember in a heated condition so that it remains in its circuit openposition, said bimetallic member being self-biased into engagement withsaid curved contact surface on said terminal and said second contactsurface rolling on said curved contact surface of said terminal memberwhen the bimetallic member is moved between its positions.

3. A current responsive circuit breaker comprising a support member,; aflat blade terminal supported by said support in cantilever fashion andhaving a curved contact surface at its free end; a second stationaryterminal supported by said support and spaced from said first terminal;a bimetallic member which is secured to said second terminal and issupported thereby in cantilever fashion, said bimetallic member having acontact surface adjacent its free end which is engageable with saidfirst terminal intermediate the ends of the later, said bimetallicmember being normally disposed in a circuit closed position in whichsaid contact surface adjacent its free end engages said terminal toprovide a conductive path between the terminals, said bimetallic memberbeing movable away from its circuit closed position toward a circuitopen position to break the conductive path therethrough in response tobeing tion and in a circuit open position, said bimetallic member beingself-biased into engagement with said curved contact surface of saidfirst terminal, said second contact portion of said printed circuitrolling on said curved free end of said first terminal when thebimetallic member is moved toward its circuit open position.

4. A current responsive circuit breaker as defined in claim 3 andwherein said printed circuit is in the form of a grid.

1? i i i i

1. A current responsive circuit breaker comprising; a terminal member; abimetallic member; one of said members being adapted to be operativelyconnected to an electrical power source; the other of said members beingadapted to be operatively connected to a load; said bimetallic memberbeing supported in cantilever fashion and having a contact surfaceadjacent its free end which is engageable with said terminal member,said bimetallic member being normally disposed in a circuit closedposition in which said contact surface adjacent its free end engages theterminal member to provide a conductive path therebetween, saidbimetallic member being movable away from said terminal member toward acircuit open position to break the conductive path therebetween inresponse to being heated by passage of a current in excess of apredetermined magnitude therethrough; a layer of electrically insulatingmaterial on a portion of said bimetallic member, a resistance heater inthe form of a printed circuit on said layer, said printed circuit havingfirst and second contact surfaces in constant engagement with a surfaceon said bimetallic member and said terminal member, respectively,whereby when said bimetallic member is in its circuit open position thecurrent is passed through said printed circuit to maintain thebimetallic member in a heated condition and in its circuit openposition, said bimetallic member being self-biased into engagement withthe terminal member and said second contact surface rolls on saidterminal member while maintaining engagement therewith when thebimetallic member moves to its circuit open position.
 2. A currentresponsive circuit breaker comprising: a terminal member; a bimetallicmember; one of said members being adapted to be operatively connected toan electrical power source; the other of said members being adapted tobe operatively connected to a load; said bimetallic member beingsupported at one end in cantilever fashion and having a contact surfaceadjacent its free end which is engageable with said terminal Member,said bimetallic member being normally disposed in a circuit closedposition in which said contact surface adjacent its free end engagessaid terminal member to provide a conductive path through the bimetallicmember, said bimetallic member being movable from said circuit closedposition toward a circuit open position in which said contact surfaceadjacent its free end disengages the terminal member to break theconductive path therethrough in response to being heated by passage of acurrent therethrough in excess of a predetermined magnitude, a layer ofelectrically insulating material on a portion of said bimetallic member,a resistance heater in the form of a printed circuit on said layer, saidterminal member having a curved contact surface, said printed circuithaving first and second contact portions in constant engagement withsaid bimetallic member and said curved contact surface on said terminal,respectively, whereby when said bimetallic member is moved toward itscircuit open position the current will be passed through the resistanceheater to maintain the bimetallic member in a heated condition so thatit remains in its circuit open position, said bimetallic member beingself-biased into engagement with said curved contact surface on saidterminal and said second contact surface rolling on said curved contactsurface of said terminal member when the bimetallic member is movedbetween its positions.
 3. A current responsive circuit breakercomprising a support member,; a flat blade terminal supported by saidsupport in cantilever fashion and having a curved contact surface at itsfree end; a second stationary terminal supported by said support andspaced from said first terminal; a bimetallic member which is secured tosaid second terminal and is supported thereby in cantilever fashion,said bimetallic member having a contact surface adjacent its free endwhich is engageable with said first terminal intermediate the ends ofthe later, said bimetallic member being normally disposed in a circuitclosed position in which said contact surface adjacent its free endengages said terminal to provide a conductive path between theterminals, said bimetallic member being movable away from its circuitclosed position toward a circuit open position to break the conductivepath therethrough in response to being heated by passage of a current inexcess of a predetermined magnitude therethrough, a layer ofelectrically insulating material on a portion of said bimetallic member,a resistance heater in the form of a printed circuit on said layer, saidprinted circuit having first and second contact surface portions inconstant engagement with said second terminal and the curved free end ofsaid first terminal, respectively, so that when said bimetallic memberis moved towards its circuit open position the current will pass throughthe resistance heater to maintain the bimetallic member in a heatedcondition and in a circuit open position, said bimetallic member beingself-biased into engagement with said curved contact surface of saidfirst terminal, said second contact portion of said printed circuitrolling on said curved free end of said first terminal when thebimetallic member is moved toward its circuit open position.
 4. Acurrent responsive circuit breaker as defined in claim 3 and whereinsaid printed circuit is in the form of a grid.